Merging Multiple Textures on a Single Model into one Mega-Texture?
So to write up an answer, the OP needed baking.

Cycles baking is a relatively simple process as far as Blender goes, and is roughly like the following:


UV Unwrap a mesh with no overlapping Islands.
Add a new, blank image in the UV/Image Editor.


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Go to the Node Editor and add an Image Texture node. Select the blank image. Do not make the image interact with the node tree in any way. Make sure the node is selected.
Go to the Properties panel > Render tab > Bake dropdown and select the following settings (for pure image textures).


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You will then have an image with all the various Image Textures mapped onto it. You can incorporate this image with UV Texture Coordinates into one mega-object material.